Beijing police have cracked the most serious gun-related case in the capital in two decades.

After receiving a tip from a navy officer, police in Beijing's Yanqing county detained five suspects and seized more than 20 guns before Spring Festival, Xinhua News Agency reported on Monday.

The navy's technical team had been inspecting the county since the end of last year to ensure residents were safe during the Spring Festival, which fell on Feb 19, the report said.